Everything I would suggest has already been said but I'll reiterate:
You can just throw everything in your pack and hope you don't forget to reattach everything to your body when you walk away from your pack. They are also not handy when you need them (like when sasquatch decides to take out all of his frustrations on you, or you need to cut a piece of cord, whichever is most likely for you in your particular area of operation).
I carry a fanny pack up front and you can attach it to the fanny pack waist strap. The fanny pack contains my PSK and rides over the top of my main packs waist belt. It only comes off when sleeping, bathing or swimming.
My favorite options are a baldric carry or a dangler. If you don't have a dedicated dangler sheath yet you can just double loop some paracord and leave it attached to your belt. Attach your sheath to the loop when you have a pack on and when you have it off too if you like a dangler. If you don't like it then you can just reattach it to your belt when you lose the pack. With either of these carry methods your fixed blade is readily accessible to live out whatever survival fantasy is running through your head at this time (it's not just me right? your guys are playing the what-if game or are dreaming of a world devoid of humans, or lost in the middle of nowhere after your plane crashes, or the zombies are coming, or something right? Right?!!)
If you're carrying a multi-tool or other folder on your belt then you can get a nylon sheath that folds fairly flat when empty and should be okay under a pack's waistbelt. When you're pack is on the knife goes in your pocket where you can still access it and when you drop the pack relocate the knife to your belt sheath.
You can also attach your folder to a piece of paracord and hang it from your belt, dangler-style, and put the knife in your pocket. This doesn't weigh your pocket down as the weight is on the belt and it leaves it readily accessible. You could just leave it dangling from your belt but having it in your pocket prevents it from flopping around.
As an aside I keep a thin belt in each of my BOBs and in my pack because I often wear climbing pants with built in belts that don't allow you to slip a sheath on. The belts are just 3/4" flat webbing with a fastex buckle that I clip around my waist sans belt loops. This allows me to attach whatever to a belt if I need too. My wife and kids rarely wear belts so they have the same belts in their BOBs and packs. The belts are actually attachment straps from REI that go for about $2 each I think, so they obviously can be used to strap things onto your pack or a tree at camp, for splints (properly padded of course so as not to cut off circulation), etc. Multi-use, negligible weight and functional.